The present invention relates to motorized servoactuators of the type employing a small, high rpm, low torque electric motor driving a train of gears to provide a low rpm, high torque output for connection to a mechanism for performing a mechanical function. Servoactuators of this type are commonly employed in automotive vehicles for controlling air valves or blend-air doors in automotive air conditioning systems; and may also be used in other applications such as heater coil water valves and valves used for control of engine coolant circulation during engine warm-up.
Heretofore, where it is desired to employ a small, high rpm, low torque motor operating on a low voltage supply such as a direct current supply operating at 12-14 volts, as typically employed in a passenger motor vehicle, problems have been encountered with noise in the gear train, due to the high rpm of the motor shaft input gear. In particular, the relatively high frequency vibration of the input stage gear causes resonance in the gear casing or housing of the servoactuator which has been transmitted to the surrounding vehicle structure, producing a noticeable and objectionable sound which is audible in the passenger compartment.
It has thus been desired to provide a motorized servoactuator capable of operating on a relatively low voltage direct current supply, and which provides a low rpm, relatively high torque output and which is quiet in the sense of being free from any audibly objectionable whine or gear noise which would be noticeably objectionable to a passenger in a vehicle.